This invention relates to intermediates useful in the preparation of pyrido[2,3-]pyrimidines, which includes N-[4-[(2-amino-4(3H)-oxopyrido[2,3-d]-pyrimidin-6-yl)methylamino]benzoyl]- L-glutamic acid (5-deazafolic acid), N-[4-[[(2-amino-4(3H)-oxopyrido[2,3-d]-pyrimidin-6-yl)methyl]methylamino]b enzoyl]-L-glutamic acid (5-deaza-N.sup.10 -methylfolic acid), N-[4-[(2,4-diaminopyrido[2,3-d]pyrimidin-6-yl)methylamino]benzoyl]-L-gluta mic acid (5-deazaaminopterin), and N-[4-[[(2,4-diaminopyrido[2,3-d]pyrimidin-6-yl)methyl]methylamino]benzoyl] -L-glutamic acid (5-deazamethotrexate). This invention also relates to processes for using said intermediates; to the novel compounds 5-deaza-N.sup.10 -substituted aminopterin and 5-deaza-N.sup.10 -substituted folic acid; and to methods for preparing such novel compounds.
Powerful dihydrofolate reductase inhibitors such as aminopterin and methotrexate are known folic acid antagonists useful in the suppression and treatment of acute leukemia and related conditions. They have as their principal mechanism of action a competitive inhibition of the enzyme dihydrofolate reductase. Folic acid and its 7,8-dihydro derivative must be reduced to tetrahydrofolic acid by this enzyme in the process of DNA synthesis and cellular reproduction. Compounds having antifolate activity such as aminopterin and methotrexate inhibit the reduction of both folic acid and 7,8-dihydrofolic acid and interfere with tissue-cell reproduction.
Several types of quinazolinyl (5,8-dideazapteridinyl) analogs of folic acid, aminopterin, and methotrexate were reported to be inhibitors both of dihydrofolate reductase and thymidylate synthetase [A. H. Calvert, T. R. Jones, P. J. Dady, b. Grzelakowska, R. M. Paine, G. A. Taylor and K. R. Harrap, Europ. J. Cancer, 16, 713 (1980); K. J. Scanlon, B. A. Moroson, J. R. Bertino and J. B. Hynes, Mol. Pharmacol., 16, 261 (1979); O. D. Bird, J. W. Vaitkus and J. Clarke, Mol. Pharmacol., 6, 573 (1970)]. Recently, N-[4-[N-[(2- amino-4-hydroxy-6-quinazolinyl)methyl]prop-2-ynyl-amino]benzoyl]-L-glutami c acid (5,8-dideaza-10-propargylfolic acid) was identified as a potent inhibitor of thymidylate synthetase [T. R. Jones, A. H. Calvert, A. L. Jackman, S. J. Brown, M. Jones and K. R. Harrap, Europ. J. Cancer, 17, 11 (1981)]. This enzyme catalyzes the de novo synthesis of thymidine nucleotides, which are required for DNA synthesis.
The synthesis of derivatives of the pyrido[2,3-d]pyrimidine ring system has been reviewed by W. J. Irwin and D. G. Wibberley, Advan. Heterocycl. Chem., 10, 149 (1969), which covers the literature to the beginning of 1968. Although many methods are reported in this review, major routes to this ring system include the cyclization of the functional derivatives of 2-aminonicotinic acids with various reagents [e.g., R. K. Robins and G. H. Hitchings, J. Am. Chem. Soc., 77, 2256 (1955)], and the reaction of derivatives of 4-aminopyrimidine with 1,3-dicarbonyl compounds or their masked derivatives [e.g., B. S. Hurlbert and B. F. Valenti, J. Med. Chem., 11, 708 (1968)]. The condensations of 4-aminopyrimidines with malondialdehyde derivatives to give pyrido[2,3-d]pyrimidines are reported by R. Bernetti, F. Mancini and C. C. Price, J. Org. Chem., 27, 2863 (1962), and B. S. Hurlbert and B. F. Valenti, J. Med. Chem., 11, 708 (1968). A procedure for the preparation of 5-oxo-(8H)-pyrido[2,3-d]pyrimidines was reported by B. H. Rizkalla and A. D. Broom, J. Org. Chem., 37, 3980 (1972). This reference discloses the following compound: ##STR3## The development of procedures for the conversion of the above compound to N-[4-[(2,4-diamino-5-oxo(8H)-pyrido[2,3-d]pyrimidin-6-yl)methylamino]benzo yl]-L-glutamic acid (5-deaza-5-oxoaminopterin), i.e., a compound having the formula: ##STR4## was reported by A. Srinivasan and A. D. Broom, J. Org. Chem., 45, 3746 (1980). In addition, N-[4-[(2-amino-4(3H)-oxo-10-formylpyrido[2,3-d]pyrimidin-6-yl)methylamino] benzoyl]-L-glutamic acid (5-deaza-10-formylfolic acid), characterized only by spectral data, was reported to be formed from 5-deazafolate and formic acid by G. K. Smith, W. T. Meuller, P. A. Benkovic and S. J. Benkovic, Biochemistry, 20, 1241 (1981). A method for preparing 5-deazafolate is not disclosed.
The inhibition of bacterial dihydrofolate reductase by pryido[2,3-d]pyrimidines has been summarized in the Advan. Heterocycl. Chem. reference. Recently, a pyrido[2,3-d]pyrimidine derivative was reported to be a potent lipid-soluble inhibitor of mammalian dihydrofolate reductase by E. M. Grivsky, S. Lee, C. W. Sigel, D. S. Duch and C. A. Nichol, J. Med. Chem., 23, 327 (1980). This reference discloses the compound: ##STR5## Other derivatives of this ring system have been evaluated for antihyptertensive activity. Thus, L. R. Bennett et al, J. Med. Chem., 24, 382 (1981) reported that the following compound lowered blood pressure in the hypertensive rat: ##STR6##
The synthesis of 5-deazafolic acid has been reported by D. T. Hurst, "An Introduction to the Chemistry and Biochemistry of Pyrimidines, Purines, and Pteridines", John Wiley and Sons, Ltd., 231 (1980). The synthesis of this compound using as an intermediate 2-amino-6-formyl-5-deazapteridine-4(3H-one, i.e., a compound having the formula: ##STR7## has been proposed by C. Temple, Jr. and J. A. Montgomery, "Synthesis of Potential Anticancer Agents", Cancer Chemotherapy National Service Center, Southern Research Institute, Progress Report 85, pages 1 and 2 (1966) and Progress Report 86, pages 8 and 10 (1967). The synthesis of 5-deazafolic acid via a condensation reaction involving triformylmethane has been reported by C. P. Tseng, Dissertation Abstracts Int. B, 40, 3752 (1980). The thesis upon which this abstract was based, C. P. Tseng, Studies in Heterocyclic Chemistry, 171-185 (1979) also describes unsuccessful work on the preparation of 5-deaza-2,4-diaminopteridine-6-carboxaldehyde dimethyl acetal, i.e., a compound having the formula: the synthesis of 5-deaza-6-formylpterin; and the conversion of this compound to 5-deazafolic acid via acetylated 5-deaza-6-formylpterin. The preparation of 5-deazaaminopterin via a long sequence of reactions involving the elaboration of a pyrimidine intermediate has been described by E. F. Elslager and J. Davoll, "Lectures in Heterocyclic Chemistry", 2, S-97, S-119-S-121 (1974).